Controlling bulk capacitance charge in a power tool device

Abstract

A power tool device including a housing, first and second battery pack terminals, at least one bulk capacitor, a pre-charge circuit, and a discharge circuit. The pre-charge circuit includes at least one resistance connected in series with the at least one bulk capacitor, and a pre-charge switch connected in series with the at least one resistance. The pre-charge switch is configured to selectively provide a conductive path to charge the at least one bulk capacitor. The discharge circuit includes a first switch and a second switch connected in series with the at least one bulk capacitor. The first switch and the second switch are configured to be turned on after the at least one bulk capacitor is charged to a DC bus voltage.

1 - 20 . (canceled) 
     
     
         21 . A power tool device comprising:
 a housing;   a positive battery pack terminal and a negative battery pack terminal;   at least one bulk capacitor;   a pre-charge circuit including:
 a constant current controller connected to the at least one bulk capacitor, the at least one bulk capacitor electrically connected between the positive battery pack terminal and the constant current controller, and 
 a pre-charge switch connected to the constant current controller, the pre-charge switch configured to selectively provide a conductive path to charge the at least one bulk capacitor; and 
   a discharge circuit including:
 a first switch and a second switch connected in series with the at least one bulk capacitor, the first switch and the second switch configured to be turned on after the at least one bulk capacitor is charged to a DC bus voltage. 
   
     
     
         22 . The power tool device of  claim 21 , further comprising:
 a discharge gate driver.   
     
     
         23 . The power tool device of  claim 22 , wherein the discharge gate driver includes an opto-coupler. 
     
     
         24 . The power tool device of  claim 23 , wherein the opto-coupler is configured to selectively connect an output charge pump signal to the discharge gate driver, wherein the discharge gate driver is configured to output a signal based on the output charge pump signal to the discharge circuit for controlling the first switch and the second switch. 
     
     
         25 . The power tool device of  claim 21 , wherein a charge current provided to the at least one bulk capacitor is limited to approximately 300 milli-amps. 
     
     
         26 . The power tool device of  claim 21 , wherein the constant current controller connected to the at least one bulk capacitor is configured to reduce a resistance in series with the at least one bulk capacitor to less than five milli-Ohms when the first switch and the second switch of the discharge circuit are turned on. 
     
     
         27 . A power tool device comprising:
 a housing;   a positive battery pack terminal and a negative battery pack terminal;   at least one bulk capacitor;   a pre-charge circuit including:
 at least one resistance connected in series with the at least one bulk capacitor, the at least one bulk capacitor electrically connected between the positive battery pack terminal and the at least one resistance, and 
 a pre-charge switch connected in series with the at least one resistance, the pre-charge switch configured to selectively provide a conductive path to charge the at least one bulk capacitor; 
   a discharge circuit including:
 a first switch and a second switch connected in series with the at least one bulk capacitor, the first switch and the second switch configured to be turned on after the at least one bulk capacitor is charged to a DC bus voltage; and 
   a first controller electrically connected to the pre-charge switch, the first controller configured to:
 send a first control signal to the pre-charge circuit to activate the pre-charge circuit by turning on the pre-charge switch, and 
 send a second control signal to the pre-charge circuit to turn off the pre-charge switch. 
   
     
     
         28 . The power tool device of  claim 27 , further comprising:
 a discharge gate driver configured to control the discharge circuit.   
     
     
         29 . The power tool device of  claim 28 , wherein the first controller is further configured to:
 send a third control signal to the discharge gate driver to turn on the first switch and the second switch of the discharge circuit; and   send a fourth control signal to the discharge gate driver to turn off the first switch and the second switch of the discharge circuit.   
     
     
         30 . The power tool device of  claim 28 , wherein the discharge gate driver includes an opto-coupler. 
     
     
         31 . The power tool device of  claim 27 , further comprising:
 a charge pump circuit.   
     
     
         32 . The power tool device of  claim 31 , further comprising:
 a second controller electrically connected to the pre-charge switch, the second controller configured to:
 send an input signal to the charge pump circuit to provide an output charge pump signal. 
   
     
     
         33 . The power tool device of  claim 32 , wherein the output charge pump signal is provided to a discharge gate driver. 
     
     
         34 . The power tool device of  claim 33 , wherein the output charge pump signal is configured to drive the first switch and the second switch. 
     
     
         35 . A capacitance control system comprising:
 a positive battery pack terminal and a negative battery pack terminal;   at least one bulk capacitor;   a pre-charge circuit including:
 at least one resistance connected in series with the at least one bulk capacitor, the at least one bulk capacitor electrically connected between the positive battery pack terminal and the at least one resistance, and 
 a pre-charge switch connected in series with the at least one resistance, the pre-charge switch configured to selectively provide a conductive path to charge the at least one bulk capacitor; and 
   a discharge circuit including:
 a first switch and a second switch connected in series with the at least one bulk capacitor, the first switch and the second switch configured to be turned on after the at least one bulk capacitor is charged to a DC bus voltage. 
   
     
     
         36 . The capacitance control system of  claim 35 , further comprising a charge pump circuit. 
     
     
         37 . The capacitance control system of  claim 35 , wherein the at least one resistance in series with the at least one bulk capacitor is reduced to less than five milli-Ohms when the first switch and the second switch of the discharge circuit are turned on. 
     
     
         38 . The capacitance control system of  claim 37 , wherein the at least one resistance in series with the at least one bulk capacitor is reduced to less than three milli-Ohms when the first switch and the second switch of the discharge circuit are turned on. 
     
     
         39 . The capacitance control system of  claim 38 , wherein the at least one resistance in series with the at least one bulk capacitor is reduced to less than two milli-Ohms when the first switch and the second switch of the discharge circuit are turned on. 
     
     
         40 . The capacitance control system of  claim 35 , wherein a current provided to the at least one bulk capacitor via the battery pack is limited to approximately 300 milli-amps.